Field
The disclosure relates to techniques to configure a start-up phase for a low drop-out (LDO) voltage regulator.
Background
Low drop-out (LDO) regulators are a type of linear voltage regulator. LDO regulators typically include a pass transistor, an error amplifier, and a resistive feedback divider. During normal operation, the pass transistor supplies current from a power supply to a load to generate a regulated voltage. The error amplifier sets the current supplied by the pass transistor to the load to be a function of the difference between the regulated voltage (as sampled by the resistive feedback divider) and a reference voltage.
In a start-up phase of the LDO regulator, the reference voltage may be brought up gradually over time from zero volts to a target voltage, e.g., the reference voltage may follow a linear ramp profile. This is done to limit undesirable inrush current from the power supply into the load during initial start-up of the LDO regulator, which may undesirably disrupt the power supply level and adversely affect other circuitry coupled to the power supply. Despite such precautions, inrush current may nevertheless be drawn from the power supply in certain scenarios. For example, if a buffer is provided between the error amplifier and the pass transistor, then the initial voltage at the output of the buffer may not be well-defined, thereby potentially causing a transient inrush current.
It would thus be desirable to provide techniques for limiting inrush current during a start-up phase of an LDO regulator.